“From crushed glass to aggregates for road construction”
How many tons of recycled glass would it take to build an emergency support for one of the busiest four-lane highways in the world? I honestly wouldn’t have a clue but I know someone that does.
Theresa Andrejack Loux is the Chief Technical Officer for AERO Aggregates, a Pennsylvania-based company with a second plant in Florida and another in California coming on stream later this year. The company takes your empty bottles and jars from recycling plants and landfill sites, turning them into an eco-friendly aggregate for use in a myriad of civil engineering applications.
Foamed Glass Aggregate (FGA) has been used as backfill in numerous projects, primarily where the soil underneath is soft and compressible and cannot support too much excess weight, such as an overnight parking apron for airplanes at Philadelphia International Airport.
In fact, it is so effective that it was being used to build up the damaged section of the Cottman Avenue exit ramp on the I-95 interstate on the outskirts of Philadelphia, which collapsed following a tanker truck fire in June this year. A staggering 215,000 cubic feet FGA was used to support a temporary, six-lane highway while contractors rebuild the actual bridge.
“FGA is absolutely ideal for this project as it only weighs around one sixth of regular soil due to it being full of air bubbles. In the case of I-95, this will help protect the ageing sewage lines running underneath the structure as they simply couldn’t withstand the weight of another 20ft of traditional soil material,” said Theresa.
“It was an awful accident and has caused huge inconvenience to everyone in the Philadelphia area so we’re just delighted we can help and get things moving again extremely quickly.”
The manufacturing process of the aggregate starts with cleaning the glass and then grinding it into a powder and subjecting it to a three-phase cleaning and filtering procedure. Workers then add a proprietary, mineral-based foaming agent and heat the powder in a kiln at 1,650 degrees Fahrenheit.
The material emerges from the kiln looking like a long, gray sheet of cake. Upon cooling, the material cracks into gravel-like pieces.
“We aim for the bulk density of our standard product to not be any heavier than 15 pounds per cubic foot, which corresponds to about 240 kilograms per cubic meter. We follow ASTM C29 standard for this type of bulk density measurement.”
“The other test that we run on a daily basis is a confined compressive strength test, which is what we use our Tinius Olsen 150ST machines for in each of our Philadelphia and Florida plants, with one on order for California. The company’s experience and input has been invaluable in developing the product from the get go and being a local company to ourselves has been an even bigger bonus.”
“The test method used for these compressive tests is EN 1097-11 although we’ve started down the road of trying to get a similar test standard in place at ASTM, which will obviously take some time.”
But where does all the required glass come from?
“Most communities do have some type of recycling program in place. Sometimes the trend in recent years has been that some communities have dropped glass from the materials that they’re collecting through single-stream programs but certainly there’s still many programs that do collect glass.”
“We work with recycling entities that are local to our plants to source the glass product that we need. We generally take lower-value glass because it’s the mixed color, the smaller pieces that generally can’t be used by a bottling operation or even a fiberglass plant. The glass product that we use generally goes to landfill if we don’t take it”
“When our California plant opens later this year, we will have the capacity to divert over 500 million bottles per year from landfill.”
It’s been an amazing journey for Aero Aggregates and a perfect example of how materials testing is vital to the development of any exciting new product. This is especially true with FGA, which can make such a huge difference to everyday life and Tinius Olsen looks forward to helping develop this material even further in the future.
Oh and it took the equivalent of 6.5 million glass bottles in FGA to build the supporting structure for the I-95 emergency repair…
for more details: Tinius Olsen
